Varieties of sighting devices are known for aiming firearms and the like. Firearms typically employ two sights that are spaced from one another along a line substantially parallel to the path along which a projectile will be discharged. A user holds the firearm manually so as to view over and/or through the two spaced sights toward the target and then discharges the firearm. The user can manually or mechanically adjust for windage and elevation. In any event, the objective is to align the firearm accurately with the target by viewing along a line to the target, as defined by the spaced sights, and holding the firearm along that line.
Among various modern sights, a special group of sights is termed red-dot sights because they project a red dot within the field of view of the sight, thereby providing the shooter with fast target acquisition. In general, all known quick-acquisition optical sights can be roughly divided into sights of an open type and sights of a closed type. The sights of the open type are those that in use are open, i.e., exposed to the surrounding atmosphere, and are closed by a separate removable cover in an inoperative condition, e.g., during transportation or storage.
A conventional quick-acquisition optical sight with a removable protective cover is shown in FIG. 1, which is a three-dimensional view of a tubular optical scope 20 that supports a quick-acquisition optical sight 22 that is provided with a removable protective cover 24, which is shown by solid lines in a disconnected state above the scope 20 and by broken lines in a scope-covering state. In the scope-covering state, the protective cover, which is molded as a single piece from a plastic material, completely covers the lens 26 and the upper surface of the sight to protect the lens and the surface of the sight against accumulation of dust, dirt, etc., on the areas that are exposed to the environment during the use. In other words, when the cover closes the sight, the sight cannot be used. An example of an open-type sight is a quick-acquisition sight known as Doctor Optics (commercially produced by American Technologies Network, California under the trademark “TA01NSN-DOC: 4x32 Trijicon ACOG®”), which is equipped with a quick-acquisition sight known as “7.0 MOA Docter®” which mounts in tandem with the Trijicon ACOG® scopes. The compact tubeless design allows for a low weight without sacrificing performance. The TA01NSN-DOC combines the technology of the battle-tested Trijicon ACOG (4x32) gun sight with the Doctor Optic 7.0 MOA Red Dot Sight. This provides the shooter with the option of quick-acquisition close-range sighting with the Doctor Sight and the precision for longer range shooting with the Trijicon ACOG 4x32. This ability to adjust to tactical situations gives the user the needed edge when lives are on the line and success is the only acceptable outcome. The ranging reticle allows for bullet-drop compensation to 600 meters without manual adjustment. The reticle appears black during the daytime and glows amber in the dark, thanks to Trijicon's patented tritium illumination. The Doctor Sight offers a large field of view due to its low magnification and is firmly factory-adjusted parallax-free to 40 yards. This adjustment ensures that parallax-related aiming errors are minimized over a long-distance range.
The optics consists of two firmly connected glass lenses. The functionally important coating reflecting the aiming dot is applied to one of the inside surfaces, which provides maximum protection against scratches. Additionally, the outer surfaces of the lenses are antireflection-coated with resistant layers. All components and mounting elements exposed to mechanical stress are made of high-grade materials, such as stainless steel and hard-anodized aluminum alloys.
An advantage of the open-type optical sights is convenience of use and aiming at the target since such sights provide a wide angle of observation and improve quick-acquisition conditions. However, the disadvantage of all open-type optical sights provided with a red-dot aiming system is that during the use, they are open to the environment and are subject to contamination with dirt, dust, and other foreign particles which under severe conditions of use may destroy the optical elements, such as diodes, or the like. In order to protect the sights of this type from contamination, they are provided with a cover, an example of which is the cover 24 shown in FIG. 1.
Red-dot-enhanced sights of a closed type are protected from contamination of optical elements by tubular housing. However, such sights are less convenient to use because they have a narrow angle of observation and are slower in acquisition of a target.
An example of an optical sight of a closed type is an internal red-dot sight disclosed in U.S. Pat. No. 7,234,265 issued in 2007 to L. Cheng, et al. The sight includes an objective lens formed from a convex lens, a planar eye lens set at a tilt angle relative to the objective lens and facing the concave surface of the objective lens, and a light-emitting device set between the planar eye lens and the objective lens and controlled to emit a point light source onto the eye lens for enabling the eye lens to reflect the point light source and to further produce a virtual point light source on the focal point of the objective lens for viewing by the user.
Another example of a closed optical sight provided with red-dot aiming features is a sight disclosed in U.S. Pat. No. 6,487,809 issued to L. Gaber in 2002. This device possesses the same drawbacks as other sights of the closed type.
Another common disadvantage of the quick-acquisition sights of all types is that they are normally not provided with optical filters; thus, aiming at a target in the direction against the sun presents a problem since the viewer is blinded. Of course, the filters can be used at any time if necessary, but such filters are not always readily available, are stored in a separate casing, and cannot be immediately attached to the lens of the sight, which sometimes may be very inconvenient in a combat situation.
The red-dot-enhanced optical sights are normally provided with a brightness-adjustment sensor, which is always in the ON condition. Sometimes, however, the scene of the target is so bright, e.g., when shooting in the direction of direct sunrays, that operation becomes useless. When the sensor is ON, it consumes a significant amount of energy of the master battery. In some situations it may be required to temporarily reduce the energy consumed by the sight sensor by closing the sensor opening, but the existing scopes are not provided with convenient means for quickly opening or closing the sensor opening. Furthermore, a removable cover can be lost because if it is not attached to the optical sight and is stored in a separate place when the latter is not in use.